Gas turbine and manufacturing process of gas turbine

ABSTRACT

The invention is intended to maintain turbine reliability when, based on a gas turbine designed for one desired cycle, a gas turbine for another different cycle is manufactured. A channel of a compressor is formed such that a mass flow of a fluid compressed by the compressor changes. Thus, when manufacturing, based on the gas turbine designed for one desired cycle, the gas turbine for another different cycle, turbine reliability can be maintained.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a gas turbine and a manufacturingprocess of a gas turbine.

2. Description of the Related Art

When a gas turbine for mixing and burning humid air and fuel ismanufactured based on a simple-cycle or combined-cycle gas turbine thathas already been designed, the mass flow of a working fluid in theturbine increases because combustion gas supplied to the turbine ishumidified. However, since a turbine output cannot be changed, the massflow of the working fluid in the compressor must be reduced.

Patent Reference 1 (JP,A 2001-271792) discloses a technique of forming alongitudinal groove to locally increase the cross-sectional area of achannel in the compressor. The provision of the longitudinal groovelocally increases the cross-sectional area of the compressor channel andlocally reduces the average Mach number of an air stream near the frontedge of a blade, thereby increasing the compressor efficiency.

SUMMARY OF THE INVENTION

However, the technique disclosed in Patent Reference 1 is just intendedto increase the compressor efficiency by locally changing thecross-sectional area of the compressor channel. In other words, reducingthe mass flow of the working fluid in the compressor is not taken intoaccount.

An object of the present invention is to maintain turbine reliabilitywhen, based on a gas turbine designed for one desired cycle, a gasturbine for another different cycle is manufactured.

To achieve the above object, the present invention is featured informing a channel of a compressor such that a mass flow of a fluidcompressed by the compressor changes.

According to the present invention, the turbine reliability can bemaintained when, based on a gas turbine designed for one desired cycle,a gas turbine for another different cycle can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an upper half of a compressor channelin a first embodiment (in the case of reducing the mass flow of aworking fluid);

FIG. 2 is a sectional view taken along the line X-X in FIG. 1;

FIG. 3 is a schematic view showing an upper half of a compressor channelin a second embodiment;

FIG. 4 is a schematic view showing an upper half of a compressor channelin a third embodiment

FIG. 5 is a schematic view showing an upper half of a compressor channelin a fourth embodiment;

FIG. 6 shows a basic construction of a simple-cycle gas turbine;

FIG. 7 illustrates a velocity triangle;

FIG. 8 is a schematic view for explaining a process of modifying a rotorblade;

FIG. 9 is a schematic view for explaining a process of modifying astator vane;

FIG. 10 is a graph representing the mass flow of a working fluid in acompressor when a humidified air turbine cycle is produced based on asimple cycle;

FIG. 11 is a diagram of the humidified air turbine cycle;

FIG. 12 is a graph representing an operating range of the compressor;

FIG. 13 is a schematic view representing a mass flow balance in thesimple cycle;

FIG. 14 is a schematic view representing a mass flow balance in thehumidified air turbine cycle;

FIGS. 15A and 15B are longitudinal and transverse sectional viewsshowing the upper half of the compressor channel shown in FIG. 1;

FIG. 16 is a sectional view showing the upper half of the compressorchannel shown in FIG. 2; and

FIG. 17 is a low-calorie blast-furnace off-gas turbine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As a gas turbine plant with high efficiency, there is known a gasturbine cycle (humidified air turbine cycle) in which humid air producedby a saturator and fuel are mixed and burnt to generate combustion gasfor rotating a turbine. FIG. 11 is a diagram of the humidified airturbine cycle. A description is first made of a flow within thehumidified air turbine cycle from a point at which the atmosphere suckedinto a compressor 1 becomes humid air to a point at which the humid airis finally discharged to the exterior. A mixer 20 sprays water 22 to theatmosphere 21 to produce humid air 5 a. The humid air 5 a produced bythe mixer 20 is compressed by the compressor 1, and the compressed airproduced by the compressor 1 is extracted through a bleed hole formedhalfway a gas path. High-pressure air 23 extracted from the compressor 1is supplied to an air cooler 27 for cooling the high-pressure air 23 byrecovered water 22 from a water recovery unit 24 and recovered water 26from a saturator 25. The high-pressure air 23 cooled by the air cooler27 is humidified by the saturator 25 using water 28 heated through theair cooler 27 and water 30 heated through an economizer 29. Humid air 31humidified by the saturator 25 is supplied to a recuperator 33 foroverheating the humid air 31 by exhaust gas 32 from a turbine 2. Then,the recuperator 33 overheats the humid air 31 supplied from thesaturator 25 to produce humid air 34 that is supplied to a combustor 3.The humid air 34 supplied to the combustor 3 is mixed with fuel 35 andburnt in the combustor 3. Produced combustion gas 36 is supplied to theturbine 2 for rotating the turbine 2. Exhaust gas 32 discharged from theturbine 2 is introduced to the recuperator 33 for heat recovery and issupplied as exhaust gas 37 to the economizer 29. The economizer 29supplies, to an exhaust gas reheater 39, exhaust gas 38 obtained afterrecovering heat from the exhaust gas 37. Exhaust gas 40 discharged fromthe exhaust gas reheater 39 is supplied to the water recovery unit 24for cooling the exhaust gas 40 by cooling water 41 to condense moistureso that water is recovered. Then, exhaust gas 42 discharged from thewater recovery unit 24 is returned to the exhaust gas reheater 39,whereby exhaust gas 43 discharged to the exterior can be prevented fromgenerating white smoke. In addition, the compressor 1 and the turbine 2are coupled to each other by an intermediate shaft, and a generator 4for converting shaft motive power produced from the turbine 2 intoelectric power is also coupled to a rotary shaft of the compressor 1.

A water circulation system will be described below. In order to supplywater to the water recovery unit 24 for cooling the exhaust gas 40 andrecovering water, a gas turbine plant of this embodiment is equippedwith a water tank 44 from which water is replenished. The waterreplenished from the water tank 44 is supplied to a cooler 45 forcooling the water. The water recovery unit 24 cools the exhaust gas 40discharged from the exhaust gas reheater 39 by the cooling water 41having been cooled, so that moisture condenses for water recovery.Further, the water discharged from the water recovery unit 24 issupplied again to the cooler 45, and is also supplied to a watertreating unit 46 in which the water is pre-treated for supply to the gasturbine. Water 22 treated by the water treating unit 46 is supplied tothe mixer 20 for spraying the water 22 into the atmosphere 21 to producethe humid air 5 a, and is also supplied to the air cooler 27 for coolingthe high-pressure air 23. Thus, the water supplied to the mixer 20 isinjected to the humid air 5 a and then supplied to the compressor 1. Onthe other hand, the water supplied to the air cooler 27 is heatedthrough the air cooler 27, and the heated water 28 is supplied to thesaturator 25. The saturator 25 employs the water 28 to humidify thehigh-pressure air 23 supplied from the air cooler 27. The water afterbeing used in the saturator 25 is supplied again to the air cooler 27,as well as to the economizer 29. In the economizer 29, the water 30discharged from the saturator 25 and flowing in the water circulationsystem is heated by the exhaust gas 37, serving as a heat source, whichis obtained after recovering heat from the exhaust gas 37 in therecuperator 33, thereby producing heated water. The thus-heated water issupplied to the saturator 25. In such a way, the heated water issupplied to the saturator 25 from not only the air cooler 27, but alsofrom the economizer 29.

When moisture is added to the high-pressure air 23 extracted from thecompressor 1 as described above, an air mass flow increases. For thatreason, when a gas turbine for the humidified air turbine cycle ismanufactured based on a gas turbine designed for a simple cycle (i.e., abase plant), the mass flow of a working fluid in the turbine (turbinemass flow) increases corresponding to the added moisture and so does agas turbine output. An increase of the gas turbine output causes thenecessity of modifying bearings and a shaft of the turbine, thegenerator, etc. Further, with an increase of the turbine mass flow, theoperating pressure ratio of the compressor coupled to the turbinethrough the intermediate shaft increases and a surge margin decreases.The compressor is a machine for boosting the pressure of a sucked fluid,and a ratio of two pressures before and after the boosting is called apressure ratio. The term “surge margin” means a margin between thepressure ratio at which a surging phenomenon occurs and the pressureratio at an actual operating point. The term “surging phenomenon” meansa phenomenon that, when the pressure ratio increases, vigorouspulsations of pressure and flow and mechanical vibrations are abruptlygenerated along with strong noises at a certain pressure ratio, and theoperation is brought into an unstable state. In other words, the gasturbine for the humidified air turbine cycle must be manufacturedwithout significantly changing the operating pressure ratio of thecompressor and the gas turbine output in the base plant.

A description is now made of a mass flow balance in each of several gasturbine cycles.

In the simple-cycle gas turbine, as shown in FIG. 13, air (atmosphere)21 sucked by a compressor 1 is compressed to produce compressed air 23.The compressed air 23 thus produced is introduced to a combustor 3 wherethe compressed air is mixed with fuel 9 and burnt to produce combustiongas 36 at high temperature and high pressure. The combustion gas 36flows into a turbine 2 for rotating the turbine 2, and a generatorcoupled to the turbine 2 generates electric power. The mass flow balancebetween the turbine and the compressor in the simple-cycle gas turbineis such that, assuming the turbine mass flow to be 100%, the mass flowof working air in the compressor is 98% and the mass flow of fuelsupplied to the combustor is 2%.

FIG. 14 represents a mass flow balance when the gas turbine for thehumidified air turbine cycle is manufactured based on the gas turbinedesigned for the simple cycle. High-pressure air extracted from thecompressor 1 is added with moisture and then introduced to the combustor3 through a recuperator 33. Therefore, the air mass flow increases 20%.In consideration of such an increase of the air mass flow, it is thebest from the viewpoints of reliability and manufacturing cost to designthe compressor such that the inlet mass flow of the compressor is 78%.With that design, neither the turbine mass flow nor the gas turbineoutput increase, and hence there is no necessity of modifying thebearings and shaft of the gas turbine, the generator, etc. Accordingly,the surge margin of the compressor can be maintained. Further, since theturbine as a high-temperature component can be the same as that in thebase plant, it is possible to reduce the manufacturing cost, cut themanufacturing steps, and ensure reliability. In addition, since the fuelmass flow in the combustor is in common to the base plant, there is nonecessity of modifying auxiliary piping for a fuel system.

A method of omitting or adding front-side stages of the compressor isknown as a practical method for changing the mass flow of the workingfluid from that in the compressor of the base plant designed for thesimple cycle. For the purpose of reducing the mass flow of the workingfluid, the front-side stages of the compressor are omitted in somecases. However, this method requires addition of many rear-side stagesto maintain matching of the operating pressure ratio of the compressorand raises a problem of increasing the cost. Also, because the mass flowof the working fluid is determined depending on the number of theomitted front-side stages, the mass flow of the working fluid requiredin the humidified air turbine cycle is not always obtained. Anotherconceivable method is to extract air from a midpoint stage or a deliveryhole of the compressor, thereby reducing the mass flow of the workingfluid introduced to the turbine. However, this method has a problem oflowering overall thermal efficiency of the gas turbine because theworking fluid having been compressed by the use of motive power isdiscarded. An additional problem is that extraction of air from themidpoint of the compressor causes mismatching between both sides beforeand after the extracting stage, thus resulting in deterioration of thecompressor efficiency. A method of modifying a plant scale is furtherconceivable. When reducing the mass flow of the working fluid in thecompressor, a new compressor may be manufactured, for example, in ascale corresponding to the root of an amount by which the mass flow isreduced from that in the base plant. With that method, however,components and drawings are not in common to those used in the baseplant.

First Embodiment

A process of manufacturing a gas turbine according to a first embodimentwill be described below. FIG. 6 shows a gas turbine plant for a simplecycle. The simple-cycle gas turbine plant comprises a compressor 1 forcompressing and delivering air (fluid) 5, a combustor 3 for receiving,as a combustion fluid, the compressed air from the compressor 1 andmixing the combustion fluid with fuel for burning, and a turbine 2rotated by combustion gas produced from the combustor 3. When the gasturbine is employed to generate electric power, the turbine 2 rotates agenerator 4 coupled to it.

A description is now made of the case of manufacturing a gas turbine fora humidified air turbine cycle from the above-described base plantdesigned for the simple cycle and including the compressor 1, thecombustor 3 and the turbine 2. In the humidified air turbine cycle thatis a highly efficient cycle utilizing moisture, as shown in FIG. 11, theatmosphere 21 supplied to the compressor 1 is humidified to produce thehumid air 5 a, and the humid air 5 a is compressed by the compressor 1.Then, the high-pressure air 23 extracted from the compressor 1 is addedwith moisture and then introduced to the combustor 3. When the gasturbine for the humidified air turbine cycle is manufactured from thebase plant that has already been designed, the mass flow of the workingfluid in the turbine 2 increases 20% corresponding to an amount ofmoisture added to the high-pressure air 23. This increases the gasturbine output and therefore causes the necessity of modifying thegenerator 4, etc. Further, because the working fluid flows through theturbine 2 at the increased mass flow, the operating pressure ratio ofthe compressor 1 increases and the surge margin decreases.

In addition, because parts of the turbine 2 operate at high temperature,e.g., 1350° C., it is desirable from the viewpoint of reliability thatthe base plant showing proved performance be employed withoutsubstantial modifications. Looking from the viewpoint of cost, theturbine 2 requires a higher manufacturing cost than the compressor 1. Inthe case of manufacturing the gas turbine for the humidified air turbinecycle from the base plant designed for the simple cycle, therefore, itis important to minimize modifications of the turbine 2 and to modifyonly the compressor 1. To avoid significant changes of the operatingpressure ratio of the compressor and the gas turbine output, the massflow of the combustion gas 36 introduced to the turbine 2 requires to beheld at a value not so different from that in the base plant. To thatend, the mass flow of the working fluid in the compressor 1 must besmaller than that in the base plant. By forming a channel in thecompressor 1 so as to reduce the mass flow of the working fluid passingthrough the channel in the compressor 1 according to this embodiment,the necessity of modifying the turbine 2 is eliminated. As a result, thegas turbine for the humidified air turbine cycle can be manufacturedwhile maintaining the turbine reliability. Further, since there is nonecessity of designing the turbine 2 from the start, the manufacturingcost can be held down.

The structure of the compressor 1 will be described below. FIG. 1 is aschematic view showing an upper half of a compressor channel. Althoughthe compressor usually comprises plural stages of stators and rotors,the stators and the rotors in intermediate stages are omitted in FIG. 1.The compressor channel in the state after omitting the stators and therotors is denoted by dotted lines. FIG. 2 is a view looking from theaxial direction of a rotary shaft of the compressor 1; namely it is asectional view taken along the line X-X in FIG. 1. The compressor 1comprises compressor rotor disks rotating with the same rotary shaft asthe turbine 2, rotor blades 13 mounted respectively to the rotatingcompressor rotor disks, and stator vanes 14 positioned between two rotorblades 13 on the upstream and downstream sides and fixed to an outercasing. In the case of employing, as the base plant, the gas turbinedesigned for the simple cycle, the channel in the compressor 1 throughwhich the air 5, serving as the working fluid, passes is formed betweenan inner surface 12 defined by an outer circumferential surface of eachcompressor rotor disk and an outer surface 11 a defined by an innercircumferential surface of the casing. In this embodiment, the distancefrom the center of the rotary shaft to the inner surface 12 at an inletof the compressor 1 is 315 mm, and the distance from the center of therotary shaft to the outer surface 11 a at the inlet of the compressor 1is 550 mm. Thus, the channel in the compressor 1 has a circular ringshape formed by the inner surface 12 and the outer surface 11 a.Further, the cross-sectional area of the channel in the compressor 1 ofthe base plant designed for the simple cycle is reduced by 0.14 m² inthis embodiment. To reduce the cross-sectional area of the channel inthe direction of the rotary shaft of the compressor in such a way, theradius from the rotation center of the compressor to the outer surface11 a is reduced by 42 mm in this embodiment by modifying the outersurface 11 a to an outer surface 11 b. In other words, the distance fromthe rotation center of the compressor 1 to the outer surface 11 b is 508mm.

A description is now made of a decrease amount a to be set when the gasturbine for the humidified air turbine cycle is manufactured from thebase plant designed for the simple cycle. The decrease amount a is setsuch that the amount by which the cross-sectional area of the channel isdecreased by reducing the radius from the rotation center of thecompressor to the outer surface 11 a substantially corresponds to theamount by which the mass flow of the working fluid flowing through thecompressor 1 is to be decreased. FIG. 10 represents the relationshipbetween the mass flow of the working fluid flowing through thecompressor 1 and the operating pressure ratio resulting when the gasturbine for the humidified air turbine cycle is manufactured from thebase plant deigned for the simple cycle. In FIG. 10, the mass flow ofthe working fluid flowing through the compressor 1 deigned for thesimple cycle and having the pressure ratio of 20 is assumed to be 1. Inthe humidified air turbine cycle, at the same pressure ratio as that inthe base plant, the mass flow of the working fluid flowing through thecompressor 1 has a smaller value, and as the pressure ratio increases,the mass flow of the working fluid also increases to approach that inthe base plant. In this embodiment, as described above, the operatingpressure ratio of the compressor 1 must be kept substantially equalbetween the simple cycle and the humidified air turbine cycle. This isbecause an increase of the operating pressure ratio of the compressor 1leads to a problem of reducing the surge margin of the compressor 1. Forthat reason, when the gas turbine for the humidified air turbine cycleis manufactured from the base plant designed for the simple cycle, themass flow of the working fluid flowing through the compressor is set to0.78 time that in the simple cycle. Accordingly, the cross-sectionalarea of the compressor channel is also set to 0.78 time that in thesimple cycle. Looking such a reduction of the cross-sectional area ofthe channel from the direction of the compressor rotary shaft, as shownin FIG. 2, the cross-sectional area of the channel in the compressordesigned for the simple cycle is reduced by a cross-sectional area A inthe circular ring form. This reduction rate corresponds to the reductionrate of the mass flow of the working fluid, i.e., 0.22. Thatrelationship is expressed by:(fluid mass flow in the humidified air turbine cycle)/(fluid mass flowin the simple cycle)=(channel cross-sectional area in the humidified airturbine cycle)/(channel cross-sectional area in the simplecycle)=0.78  (Eq. 1)Therefore, the decrease amount a by which the radius from the rotationcenter of the compressor to the outer surface 11 a is to be reduced canbe determined from both the above reduction rate of the channelcross-sectional area and the distance from the rotation center of thecompressor to the inner surface. In some of plants to be manufactured,the amount of air extracted from the base plant is changed. However, thechange of the mass flow of the working fluid in the compressor shouldalso be taken into consideration to change the channel cross-sectionalarea when determining the decrease amount a by which the radius from therotation center of the compressor to the outer surface 11 a is to bereduced. Further, when the mass flow of the working fluid is not fairlychanged, the decrease amount a in the rear-stage side can be set to asmall value, and a significant influence is not produced in some caseseven if the outer surface is not modified. In such a case, the radiusfrom the rotation center of the compressor to the outer surface 11 a maybe reduced only in the front-stage side, and the rear-stage side mayremain the same as that in the base plant.

FIG. 1 shows an example in which, in similar stages to those in the baseplant, the inner surface and the outer surface both forming the channelare represented by straight-line segments like kinked lines. The numberof the straight-line segments is preferably increased as many aspossible so that the change of the mass flow of the working fluid andthe change of the channel cross-sectional area do not fluctuate from oneto another stage.

By reducing the radius from the rotation center of the compressor to theouter surface 11 a for modification to the outer surface 11 b as in thisembodiment, inner-side components, such as rotor disks, can be shared bythe gas turbine plant of this embodiment and the base plant. Also, aworkpiece material of the casing as one of outer-side components can beused in common to the base plant and can be adapted for the gas turbineplant, in which the mass flow of the working fluid in the compressor isreduced, by decreasing an amount by which the workpiece material is tobe cut. Thus, the modification from the base plant can be minimized.Further, since the mass flow of the working fluid in the compressor canbe changed by altering the distance between the inner surface and theouter surface of the compressor, there is no necessity of newlydeveloping a compressor that can achieve a inlet mass flow suitable forthe humidified air turbine cycle. As a result, the modification of thecompressor can be minimized. Moreover, by utilizing, as a base, thecompressor plant having already been designed and showing provedperformance, it is possible to avoid a risk in newly developing acompressor that has a narrow operating range as shown in FIG. 12 andhence faces a difficulty in aerodynamic design. FIG. 12 is a graphrepresenting a range where the compressor is operable. In the graph ofFIG. 12, the horizontal axis represents an inlet flow angle, and thevertical axis represents a loss coefficient. As seen from FIG. 12, theoperating range where the loss coefficient is small and the compressoris operable is very narrow. Further, the development cost can be cut ascompared with the case of developing the gas turbine plant from thestart. Additionally, components can be used in common to the compressorof the base plant.

As described above, since the inner-side components, such as the rotordisks, can be used in common by reducing the radius from the rotationcenter of the compressor to the outer surface 11 a for modification tothe outer surface 11 b, the manufacturing steps can be cut. Also, sincethe structure of the compressor rotor disks is shared by the gas turbineplant of this embodiment and the base plant, reliability can also beimproved. Further, since auxiliary piping constituting the fuel systemfor the combustor to which the fuel is supplied can be used in common tothe base plant, a reduction of the manufacturing cost is resulted.

A process of modifying a blade (vane) shape to reduce thecross-sectional area of the channel in the compressor 1 will bedescribed below. FIGS. 8 and 9 illustrate processes of modifying bladeand vane shapes, respectively, when the gas turbine for the humidifiedair turbine cycle is manufactured from the stator vanes and the rotorblades of the compressor in the base plant designed for the simplecycle. In this embodiment, the compressor blades (vanes) in the baseplant are each partly cut. More specifically, when the mass flow of theworking fluid in the compressor is decreased by reducing the radius fromthe rotation center of the compressor to the outer surface 11 a, a tipportion of the rotor blade on the outer side is cut and a root portionof the stator vane on the outer side is cut as shown in FIGS. 8 and 9.Because combustion gas at high temperature flows through a turbine, aturbine blade (vane) is manufactured by precision casting. Therefore,once the blade (vane) shape is altered, design of the blade (vane) mustbe restarted from the beginning. On the other hand, in the case of acompressor, the compressor blade (vane) is manufactured by cutting orforging one workpiece material. For that reason, it is relatively easyto manufacture a compressor blade (vane) in the form obtained by partlycutting another one. Accordingly, the compressor blade (vane) for thehumidified air turbine cycle can be manufactured in a short time fromthe compressor blade (vane) for the simple cycle.

The length by which the blade (vane) is to be cut is substantially equalto the decrease amount a described above. By modifying the blade (vane)shape in such a manner, the cross-section of the compressor blade (vane)for the simple cycle and the cross-section of the compressor blade(vane) for the humidified air turbine cycle are kept substantially thesame at an equal radius Y from the rotation center of the compressor. Ifthe cross-sectional shape of the blade (vane) is the same betweendifference cycles in blade (vane) positions at an equal radius from therotation center of the compressor, the rotating velocity and thevelocity triangle are also the same in the respective cross-sections.Therefore, the axial flow velocity in the compressor is the same and sois the mass flow of the working fluid in the respective cross-sections.Stated another way, the mass flow of the working fluid can be increasedor decreased corresponding to the amount by which the cross-sectionalarea of the channel has been cut or increased, without appreciablychanging the compressor performance, such as efficiency.

The velocity triangle will be described below. FIG. 7 illustrates avelocity triangle when a rotor blade train 13 a is rotated in a certaindirection. An axial compressor is made up of multiple stages eachcomprising a rotor blade and a stator vane. A triangle constituted bythree vectors, i.e., an absolute velocity vector 15, a relative velocityvector 16 and a rotating velocity 17, at each of an inlet and an outletof one blade (vane) is called a velocity triangle. For the sake ofsimplicity, a description is herein made on an assumption that the inlettemperature, the number of rotations, and the rotating velocity are allconstant. Generally, in the axial compressor, because the range of inletflow angle where the blade (vane) operates is narrow, the shape of thevelocity triangle is not so changed. Therefore, if the blade (vane) isthe same and the radius from the rotation center of the compressor isalso the same, the rotating velocity and the velocity triangle are thesame in respective cross-sections. Accordingly, the axial flow velocityin the compressor is the same and so is the mass flow of the workingfluid passing the respective cross-sections. In practice, the velocitytriangle for each stage is adjusted through matching over all thestages, and the gas turbine is operated at the mass flow of the workingfluid at which matching is maintained over all the stages. Statedanother way, according to the process of reducing or enlarging thechannel in the base plant to modify the inlet mass flow of thecompressor from that of the base plant as in this embodiment, the blade(vane) has the same shape as that in the base plant in a most part ofthe channel. As a result, the velocity triangle in each cross-sectiondoes not change from that in the base plant, and the mass flow of theworking fluid can be increased or decreased corresponding to the amountby which the channel has been reduced or enlarged, without accompanyingan appreciable change of performance, such as efficiency.

In practical manufacturing, the blade (vane) may be formed whileadjusting the blade (vane) in the base plant, taking into account that aflow field is changed due to the channel portion reduced or enlargedfrom that in the base plant. For example, a cross-section of the tip orroot of the blade (vane) may be twisted to control a secondary flow. Inthis embodiment, to reduce the radius from the rotation center of thecompressor to the outer surface 11 a and hence to decrease the mass flowof the working fluid, the tip portion of the rotor blade is cut.Further, the root portion of the stator vane on the outer side is cut.As an alternative, it is instead conceivable to cut a tip portion of thestator vane on the inner side by the decrease amount a without changingthe vane shape near the root. However, this modification leads to areduction of performance because the rotor blade has the samecross-section as that in the base plant at an equal radius from therotation center of the compressor, but the stator vane has a differentcross-section from that in the base plant. In any case, since the blade(vane) length is changed and the natural frequency of the blade (vane)is also changed, design for anti-resonance must be performed again.

Furthermore, when a low-calorie blast-furnace off-gas turbine ismanufactured from the base plant designed for the simple cycle, the fuelmass flow is increased from that in the base plant. Accordingly, themass flow of the working fluid in the turbine is relatively increasedfrom that in the compressor in comparison with the base plant. To avoidsignificant changes of the operating pressure ratio of the compressorand the gas turbine output, therefore, the mass flow of the workingfluid in the compressor 1 must be reduced from that in the base plant bythe process according to this first embodiment, etc. without appreciablychanging the mass flow of the working fluid in the turbine 2 from thatin the base plant.

The term “low-calorie blast-furnace off-gas turbine” means a system inwhich blast-furnace off-gas produced from an iron mill is employed asfuel for a gas turbine to generate electric power. As shown in FIG. 17,byproduct gas, e.g., blast-furnace off-gas 47 produced from an ironmill, is compressed by a booster compressor 48, and the boostedblast-furnace off-gas is introduced as fuel 50 to a combustor 3. In thecombustor 3, air 23 compressed by a compressor 1 and the fuel 50 aremixed with each other and then burnt to produce high-temperature gas 36.A turbine 2 is rotated by the high-temperature gas 36, and a generatoris rotated by shaft motive power produced from the turbine 2, therebygenerating electric power.

The blast-furnace off-gas used in such a system has a low calorie value,and therefore a large amount of the blast-furnace off-gas is required asfuel for the gas turbine in order to obtain a predetermined turbineoutput. Also, in order to mix the blast-furnace off-gas with the airboosted by the compressor and to produce gas at the predetermined hightemperature and high pressure in the combustor, the blast-furnaceoff-gas introduced to the combustor must be boosted in advance by, e.g.,the booster compressor.

When the low-calorie blast-furnace off-gas turbine is manufactured fromthe base plant designed for the simple cycle, the fuel mass flow isincreased about 30 to 40% from that in the base plant. Accordingly, themass flow of the working fluid in the turbine is relatively increasedfrom that in the compressor in comparison with the base plant. To avoidsignificant changes of the operating pressure ratio of the compressorand the gas turbine output, therefore, the mass flow of the workingfluid in the compressor must be reduced from that in the base plantwithout appreciably changing the mass flow of the working fluid in theturbine from that in the base plant. In that low-calorie blast-furnaceoff-gas turbine, since the fuel mass flow increases, piping for a fuelsystem must be modified to have a larger diameter than in the baseplant. Moreover, additional auxiliaries, such as the booster compressorfor boosting the blast-furnace off-gas, are also required.

In an exhaust-gas recirculation gas turbine of the type that exhaust gasis boosted by a separate compressor and introduced to the combustor 3instead of recirculating the exhaust gas to the inlet side of thecompressor 1, when a gas turbine designed for the simple cycle isemployed as the base plant, it is required to reduce the mass flow ofair sucked by the compressor 1 by the process according to the firstembodiment, etc., or to reduce the mass flow of the exhaust gasrecirculated to the combustor 3. However, the process of reducing themass flow of the exhaust gas recirculated to the combustor 3 lessens theeffect of recirculation. For that reason, the process according to thefirst embodiment is more effective.

Second Embodiment

FIG. 3 shows an upper half of a compressor channel in a secondembodiment. In FIG. 3, as in FIG. 1, the compressor channel inintermediate stages is denoted by dotted lines. In the secondembodiment, as in the first embodiment, the mass flow of the workingfluid in the compressor 1 is reduced when a gas turbine for a differentgas turbine cycle is manufactured from the base plant designed for onedesired gas turbine cycle and comprising the compressor 1, the combustor3 and the turbine 2. More specifically, in this embodiment, the massflow of the working fluid in the compressor 1 is reduced by increasingthe radius from the rotation center of the compressor to an innersurface 12 a by an amount b such that a new inner surface 12 b isformed. With this embodiment, the inner-side components, such as thecompressor rotor disks, cannot be used in common, but the outer-sidecomponents, such as the casing, can be used in common.

In the case of reducing the mass flow of the working fluid in thecompressor 1, it is also feasible to reduce the radius from the rotationcenter of the compressor to the outer surface and to increase the radiusfrom the rotation center of the compressor to the inner surface at thesame time instead of either reducing the radius from the rotation centerof the compressor to the outer surface as in the first embodiment orincreasing the radius from the rotation center of the compressor to theinner surface as in the second embodiment. This method makes smaller theamounts by which the inner and outer surfaces of the compressor channelare to be changed, in comparison with the case of reducing the mass flowof the working fluid by modifying only one of the inner and outersurfaces. As a result, a change of the secondary flow caused by theendwall of the compressor can be reduced with respect to the secondaryflow in the base plant. Another conceivable method of decreasing themass flow of the working fluid by reducing the cross-sectional area ofthe channel is to reduce both the radius from the rotation center of thecompressor to the inner surface and the radius from the rotation centerof the compressor to the outer surface.

Third Embodiment

FIG. 4 shows an upper half of a compressor channel in a thirdembodiment. In FIG. 4, as in FIG. 1, the compressor channel inintermediate stages is denoted by dotted lines. In the third embodiment,contrary to the first embodiment, the mass flow of the working fluid inthe compressor 1 is increased when a gas turbine for a different gasturbine cycle is manufactured from the base plant designed for onedesired gas turbine cycle and comprising the compressor 1, the combustor3 and the turbine 2. More specifically, in this embodiment, the massflow of the working fluid in the compressor 1 is increased by increasingthe radius from the rotation center of the compressor to the outersurface 11 a by an amount c such that a new outer surface 11 b isformed. Since each of the rotor blades 13 in an area where thecompressor channel is enlarged has a larger rotating velocity, theeffect of reducing a blade load is obtained and the efficiency isincreased to some extent. Also, a workpiece material of the casing asone of the outer-side components can be used in common to the base plantand can be adapted for the gas turbine plant, in which the mass flow ofthe working fluid in the compressor is increased, by increasing anamount by which the workpiece material is to be cut. Thus, themodification from the base plant can be minimized.

Further, in some cases, the inlet mass flow of the compressor 1 isincreased to increase the output of a gas turbine under development. Insuch a case, the mass flow of the working fluid in the compressor can beincreased without changing performance, such as efficiency, byincreasing the radius from the rotation center of the compressor to theouter surface as in this embodiment.

Fourth Embodiment

FIG. 5 shows an upper half of a compressor channel in a fourthembodiment. In FIG. 5, as in FIG. 1, the compressor channel inintermediate stages is denoted by dotted lines. The fourth embodimentrepresents the case in which the mass flow of the working fluid in thecompressor 1 is increased as in the third embodiment. More specifically,the mass flow of the working fluid in the compressor 1 is increased byreducing the radius from the rotation center of the compressor to theinner surface 12 a by an amount d such that a new inner surface 12 b isformed. With this embodiment, the mass flow of the working fluid in thecompressor 1 can be increased even in the case that the casing requiresto be used in common and the process according to the third embodimentcannot be employed because of a too small thickness of the casing.

In the case of increasing the mass flow of the working fluid in thecompressor 1, it is also feasible to increase the radius from therotation center of the compressor to the outer surface and to reduce theradius from the rotation center of the compressor to the inner surfaceat the same time instead of either increasing the radius from therotation center of the compressor to the outer surface as in the thirdembodiment or reducing the radius from the rotation center of thecompressor to the inner surface as in the fourth embodiment. This methodmakes smaller the amounts by which the inner and outer surfaces of thecompressor channel are to be changed, in comparison with the case ofincreasing the mass flow of the working fluid by modifying only one ofthe inner and outer surfaces. As a result, a change of the secondaryflow caused by the endwall of the compressor can be reduced with respectto the secondary flow in the base plant. Another conceivable method ofincreasing the mass flow of the working fluid by increasing thecross-sectional area of the channel is to increase both the radius fromthe rotation center of the compressor to the inner surface and theradius from the rotation center of the compressor to the outer surface.In this case, the radius from the rotation center of the compressor tothe outer surface must be further increased in comparison with the caseof increasing only that radius. However, since the average rotatingvelocity is increased, the blade load is reduced and the efficiency canbe increased.

Fifth Embodiment

FIGS. 15 and 16 show a sectional structure of an upper half of a channelin an axial compressor 1. The compressor channel is a ring-shapedchannel defined by compressor rotor disks 23 rotating with the samerotary shaft as a turbine, and a casing 22 disposed around thecompressor rotor disks 23 to constitute the stationary side. Rotorblades 13 are fixedly mounted to an inner surface 12 of the compressorchannel, which is defined by the rotating compressor rotor disks, andstator vanes 14 are fixedly mounted to an outer surface 11 of thecompressor channel, which is defined by the casing, such that eachstator vane is positioned between two adjacent rotor blades 13 on theupstream and downstream sides. In a multistage axial compressor, eachstage comprises a pair of the rotor blade 13 mounted to a rotary shaftand the stator vane 14 mounted to the casing. The multistage axialcompressor sucks air (atmosphere) and compresses the sucked air throughsuccessive stages to predetermined pressure, thereby producinghigh-pressure air.

FIG. 15A shows the compressor channel of FIG. 1 in more detail on anassumption that the channel has a linear shape. In particular, FIG. 15Ashows four stages of the compressor 1 near its final stage. In asimple-cycle gas turbine, a compressed fluid 6 is introduced to thecombustor 3. The stator vane 14 is mounted to the casing 22 with the aidof a dovetail 21. The rotor blade 13 is mounted to the rotor disk 23with the aid of a dovetail 21. Note that the dovetail 21 of the rotorblade 13 does not appear in a cross-section of FIG. 15A, and thereforeit is not shown in FIG. 15A. When a gas turbine for the humidified airturbine cycle is manufactured by modifying an outer surface 11 a of thechannel in the base plant designed for the simple cycle, the radius fromthe rotation center of the compressor to the outer surface 11 a isreduced such that a new outer surface 11 b is formed. FIG. 15B shows apart of the sectional structure in FIG. 15A, looking from a cylindercross-section perpendicular to the rotary shaft. As seen from FIG. 15B,a height H0 of the outer surface 11 a is reduced to a height H1 of theouter surface 11 b. For such a modification, a vane portion of thestator vane 14 is cut and the position of the dovetail 21 of the statorvane 14 is lowered as viewed in FIGS. 15A and 15B. At that occasion, bycutting the stator vane 14 such that the shape of the stator vane 14until the height H1 remains the same as the vane shape in the base plantuntil the height H1, the velocity triangle is held the same, asdescribed above, in respective vane cross-sections between the baseplant designed for the simple cycle and the gas turbine for thehumidified air turbine cycle.

FIG. 16 shows the compressor channel of FIG. 2 in more detail on anassumption that the channel has a linear shape as in FIG. 15. Inparticular, FIG. 16 shows four stages of the compressor 1 near its finalstage. When a gas turbine for the humidified air turbine cycle ismanufactured by modifying an inner surface 12 a of the channel in thebase plant designed for the simple cycle, the radius from the rotationcenter of the compressor to the inner surface 12 a is increased suchthat a new inner surface 12 b is formed. For such a modification, in thecase of FIG. 16, a blade portion of the rotor blade 13 is cut and theposition of the dovetail 21 (not shown) of the rotor blade 13 is raisedas viewed in FIG. 16. At that occasion, by cutting the rotor blade 13 asin the above case of FIG. 15 such that the shape of the remaining rotorblade having been not cut remains the same as the blade shape in thebase plant, the velocity triangle is held the same, as described above,in respective blade cross-sections between the base plant designed forthe simple cycle and the gas turbine for the humidified air turbinecycle.

1. A manufacturing process of a gas turbine for use in manufacturing agas turbine from a base plant comprising a gas turbine designed for onedesired gas turbine cycle and including a compressor with a channel tocompress a fluid flowing inside a casing to which stator vanes arefixed, said manufactured gas turbine having a different gas turbinecycle, said process comprising the steps of: forming said compressorchannel for the fluid to have an inner surface defined by an outercircumferential surface of each of compressor rotor disks and an outersurface defined by an inner circumferential surface of said casing,changing the distance between said inner surface and said outer surfacein comparison with a corresponding distance in said base plant withoutdeleting or adding stages of said compressor, and cutting a tip portionof a rotor blade or a root portion of said stator vane by a lengthsubstantially equal to an amount by which the radius from a rotationshaft center of said compressor to said outer surface has been reduced.2. A manufacturing process of a gas turbine that is manufactured withrespect to a first gas turbine from a base plant having one desired gasturbine cycle, said manufactured gas turbine including a compressor, thecompressor having compressor rotor disks, a casing to which stator vanesare fixed and a channel for compressing a fluid flowing inside thecasing, wherein the manufactured gas turbine has a gas turbine cyclethat is different from said one gas turbine cycle, said processingcomprising the steps of: forming said compressor channel for the fluidto have an inner surface defined by an outer circumferential surface ofeach of said compressor rotor disks and an outer surface defined by aninner circumferential surface of said casing, changing the distancebetween said inner surface and said outer surface in comparison with thecorresponding distance in said base plant such that a mass flow of thefluid passing through said compressor channel is different from that ofa comparable channel of a compressor of said one gas turbine cyclewithout deleting or adding stages for said compressor, and cutting a tipportion of a roto blade or a root portion of said stator vane by alength substantially equal to an amount by which a radius from therotation shaft center of said compressor to said outer surface has beenreduced.